Along x-axis temperature. And along y-axis the sensing response. What formula should I employ for the y-axis plot?
Typically, sensor response data will be represented as a relative response:
Relative Sensor Response = (X - Y) / Y
X = the maximum value of your sensor's measured response parameter (Voltage, Current, etc) in the presence of the analyte.
Y = the initial value of your sensor's measured response parameter in the absence of the analyte.
It is also common to present the relative sensor response as a percentage.
Please refer to our work on chemiresistor sensors as a guide:
http://pubs.rsc.org/en/Content/ArticleLanding/2012/LC/C2lc40575j#!divAbstract
Generally the gas sensing response has been calculated through sensitivity formula,
S=(A-B)/B, where A is a change in resistance in air ambience,B is a change in resistance in exposed gas.so for that the calculated sensitivity results were plotted at y-axis and corresponding temperature were plotted at x-axis.
Dear Mr. Sandi P choudhury,
You will find all the details in the following two papers published by one of my students on the gas sensing properties of SnO2 films for H2S gas.
Arijit Chowdhuri et al., Applied Physics Letters, volu 84, No.7 , year 2004, page No. 1180-1182.
Arijit Chowdhuri et al., Sensorsw and Actuators, Vol. 93, Issues 1-3, year 2003, page Nos. 572-579
Prof. K. sreenivas
gas sensor response needs to be measured with a automatic logging meter which can record the changing values of the resistance of the gas sensor with time.
Lets say your sensor gives a maximum responsivity at a temperature of 250 deg c.
Then set this temperature, and have a valve in your chamber which inlets the gas to be detected. This is gas ON condition Now start measuring the changes in resistnce with time, Then suddenly witch off, or close the vale (Gas off condition). Keep monitoring the changes in the resistance of your sensor, it showld now recover back to the same resistance value, which it had when the gas was not present.
The two paper I have cited in my previous mail, clearly explain how the gas response speed and recovery were measured with a very simple auto logging multimeter, purchae for about Rs 10,000 in the local Delhi market.\Nowadays you have more sophisticated meters.
K. Sreenivas
Thank you all. Thank u Sreenivas Sir. I will go through the papers and would seek more of your advice if I come across a barrier... Thanks and Regards
Hi Sandip,
I hope your problem has been solved now, but for your information, mostly for a n-type sensing material in a reducing gas, the gas response is calculated as the ratio of the resistance of the sensor in air to the resistance in the gas (response = Ra/Rg) while in an oxidizing gas, it is Rg/Ra. You can use the values of current and conductance as well instead of resistance depending on your sensing system and the values of Ra and Rg can be easily measured by sensing or response curve.
Dear Sandip Pchoudhury
In the following we will use the terms “response” and
“sensitivity” synonymously. Mathematically the response S
is defined as follows:
S = R0/Rgas − 1
where R0 is the sensor resistance in clean air and Rgas is the
sensor resistance under the influence of a reducing gas. as in the paper with the link below.
https://pdfs.semanticscholar.org/0a40/75c6db5076363c70b526f2bb489cdea5ffb8.pdf.
Best regards
1. In the gas sensing mechanism, resistance and response both the term are proportional? because those are frequently used.
2. In the gas sensing mechanism, how the thickness of the depletion layer increases gas sensitivity increases? Please help me to understand.
Dear Mr. Sandip Pchoudhury ,
I suggest the following route,
1. Finding out response type
2. Understanding out baseline drift
3. Quantifying the results
4. Graphical representation of the results based on the definition of applied and pure chemistry sensor sensitivity definition.
Please see the attached papers for definition of #3 and #4 in the above given list.
Thanks
Regards
Engin
I have a follow up question. Why most of the literature on MOS gas sensors use S=Rg/Ra or Ra/Rg to calculate response whereas 2D materials based sensor uses response%=(Ig-Ia/Ia) instead of response. The use of response % is more logical to me than response. Please leave your opinion to make it more clear. Thank you.
The sensors including the gas sensor converts a nonelectrical property x to an electrical property y. So, the response of the sensor is y=f(x). For the gas sensor for example the gas concentration N=x and the y= R the resistance of the sensor.
So the response of the sensor is R= f(N). There are factors which affects such response such as the type of the gas and the temperature. So, the response must be determined at a given temperature and gas type.
You can plot R as a function of temperature T for the same gas type and concentration.
But when you measure the response of the sensor to the as a gas sensor you must keep T=consatnt and the type of the gas.
Best wishes.
You can measure the gas response on y axis with the formula VG-VA/Vg * 100 in percent
Response; it is the amount of change of the physical parameter in the presence of a certain concentration of gas.
Sensitivity; it is the response rate to the unit of concentration of the targeted gas.
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